1. Field of the Invention
The invention generally relates to woodworking and to shaping machines, especially to grooving machines. More specifically, the invention relates to a process of woodworking involving mechanical cutting or shaping, especially to a process for cutting using a templet or pattern. The invention also relates to milling and to a templet tracer or cutter. In a specific application, the invention is a guide for use with a tool cutting a linear groove.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98
One of the chief uses for a shaping tool such as a saw or router in woodworking is to cut a straight groove. Circular saws and routers often are distinguished as separate tools, but both are able to cut a straight groove. Each tool carries a tool head at a predetermined position, such as at the end of a motor shaft. The tool performs work by spinning the tool head, which has the general shape of a cylinder with a series of chisel edges on its circumferential surface.
The spinning cylindrical tool head is connected to a power driven motor, such as an electric motor, by a chuck or other connector for the appropriate tool head. Each tool head can be attached to an end of the motor shaft so that it spins at the same speed as the motor, or it can be driven by an intermediate drive mechanism to spin at a different speed. Both types of tool can be equipped with a support plate for establishing a spacing or supported position between the workpiece and the tool head while the tool head performs its work. In hand held tools, the support plate is between the motor housing and the tool head. In mounted tools such as a radial arm saw, table saw, or table mounted router, the support plate is an underlying table. The support plate of a circular saw is parallel to the motor axis, while the support plate of a router is perpendicular to the motor axis.
The tool head of a router often is a generally cylindrical bit, with a relatively long cylinder axis as compared to a circular saw blade. The router bit has a relatively short cylinder diameter as compared to a circular saw blade. A router bit commonly is about one-half or three-fourths inch in diameter, although the diameter may vary within a single bit to enable the router to produce an ornate pattern on a workpiece. However, a bit in the shape of a cylinder is useful to cut a groove equal to the diameter of the cylinder into a workpiece. A router can selectively axially extend the bit beyond the support plate of the router, along the axis of the cylindrical bit or motor shaft for variable engagement with the workpiece. The bit is extended over a preselected range of engagement with the workpiece to cut a groove of any desired depth with the preselected range.
The tool head of a circular saw is a generally cylindrical blade, with a cylinder axis of only about one-eighth inch. The diameter of the saw blade is many times greater than that of a typical router bit. Circular saw blades often have a diameter of several inches with popular diameters ranging from about seven to ten inches. The blade can be extended through the support plate of the saw within a preselected range along the radius of the cylindrical blade and perpendicular to the axis of the motor housing, rather than along the axis of the cylinder as done in a router. In this way, the saw blade cuts into a workpiece by a preselected radial depth. A saw often is used to cut through the entire thickness of a workpiece to sever it, but a circular saw blade can cut a groove of less depth than the full thickness of the workpiece by appropriate radial adjustment of the blade with respect to the support plate. The width of the groove can be made wider than the typical one-eighth inch thickness of a blade making repeated adjacent cuts or by using a wider blade or assembly of several blades.
The sameness between a router and a circular saw is significant because other similar shaping tools exist but are given special names. Regardless of the name used, shaping tools frequently share the general characteristic of spinning a cylinder with chisel teeth on its circumference. This type of tool is within the category of shaping tools, regardless of the specific name applied to it.
Linear grooves are given different names according to their shape and purpose. These include the mortise, which is usually a rectangular cavity in wood or other material that is prepared to receive a tenon. Another type of straight groove is a rabbet, which is a cut along or near the edge of a piece of wood that allows another piece to fit into it to form a joint. Still another variety of groove is a dado, which is a rectangular groove cut into a board so that a like piece may be fitted into it. Straight grooves are used due to the ease of measurement, fabrication, and assembly of mating straight edges.
Fabricating a straight groove can be difficult when the groove is significant in length. In a professional woodworking shop, large scale equipment is used to guide the necessary tooling and the workpiece with respect to each other. However, such equipment is costly, and its size can be prohibitively large.
Various types of guides are used to cut a straight groove in a workpiece. A straightedge can be clamped to a workpiece and the tool moved along it in a straight line. Alternatively, the tool can be mounted to a table with a straightedge or fence also attached to the table to guide the workpiece. A tool can carry an adjustable spacer arm with an edge guide on its end. These types of guides are useful but not always practical, especially when the groove is spaced by a considerable distance from the nearest parallel edge of the workpiece.
It would be desirable to have a linear guide for shaping tools that is small in size. Similarly, it would be desirable to have a linear guide for shaping tools that is simple in construction while it enables forming a straight cut of considerable length.
To achieve the foregoing and other objects and in accordance with the purpose of the present invention, as embodied and broadly described herein, the method and apparatus of this invention may comprise the following.
Against the described background, it is therefore a general object of the invention to provide an improved apparatus and method for cutting a straight groove in wood or other materials.
A more specific object is to enable a shaping tool such as a router or circular saw to form a cut in a straight line. Such a cut may be a shaped groove such as a mortise, dado, rabbet, or saw cut of almost any length.
Additional objects, advantages and novel features of the invention shall be set forth in part in the description that follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by the practice of the invention.
According to the invention, a guide is suited to direct a power driven shaping tool adapted to carry a tool head in a predetermined position for movement along a linear axis of movement. The guide is formed of a first plate having first and second opposite faces that are positioned parallel to the linear axis of movement. The first plate defines a tool head aperture that passes through the first and second faces of the plate. A connecting device on the first plate is positioned to attach a shaping tool to the first side of the first plate in a position where a tool head carried by the shaping tool is aligned for passage through the tool head aperture. The first plate is guided for movement along the linear axis of movement One mechanism for guiding is a longitudinally elongated channel follower positioned parallel to the linear axis of movement, aligned with the tool head aperture, and extending from the second face of the first plate. Another mechanism for guiding is a plurality of juxtaposed guiding members joined in a linearly extendable series by pivots operating on parallel axes, interconnecting the guiding members. The guiding members are moveable along the axis of movement between a folded position and an extended position. A guiding member on a leading end of the linear series is pivotally joined to the first plate, and a guiding member located on a trailing end of the linear series carries an anchor for attachment to an external surface. The two guiding members can be used together.
According to a further aspect, the guide may include a second plate having first and second opposite faces positioned parallel to the linear axis of movement. The first face of the second plate faces the second face of the first plate. The second plate defines a longitudinally elongated channel in its first face, positioned parallel to the linear axis of movement, and sized to receive the channel follower.
The accompanying drawing, which is incorporated in and forms a part of the specification illustrates preferred embodiments of the present invention, and together with the description, serves to explain the principles of the invention. In the drawing: